1. Field of the Invention
The invention relates in general to elevator systems, and more specifically to elevator systems which include controls for detecting damage to the elevator system, such as caused by an earthquake, and then modifying the operation of the elevator system.
2. Description of the Prior Art
U.S. Pat. No. 3,792,759, which is assigned to the same assignee as the present application discloses a dual level detector arrangement for an elevator system in which at least the first level of detection is responsive to acceleration forces applied to the associated building. The two detection levels are arranged to provide an early warning of earthquake, without nuisance service outages. The second level of detection may be responsive to acceleration forces of a higher magnitude than the first level of detection, or it may be responsive to mechanical damage to the elevator system such as displacement of the counterweight from its guides.
U.S. Pat. Nos. 3,783,978; 3,791,490; 3,815,710; and 3,896,906 disclose different arrangements for detecting damage to an elevator system, which include (a) detecting the interruption of a sliding or rolling electrical contact maintained between a movable component of the elevator system and a wire or track in the hoistway, (b) detecting the mechanical contact between a conductive ring disposed on a movable component of the elevator system and a vertical wire which extends the length of the hoistway on the center line of the conductive ring, and (c) detecting mechanical contact between a plumb bob and an encircling metallic ring arrangement, both of which are carried by one of the movable components of the elevator system. Copending application Ser. No. 584,431 filed June 6, 1975, now U.S. Pat. No. 4,011,928, which is assigned to the same assignee as the present application, discloses a damage detector for an elevator system which utilizes a transmitter of radio frequency energy and a receiver therefor.
Our copending application Ser. No. 693,986, filed June 8, 1976, entitled "Elevator System" discloses a damage detector which utilizes inductive coupling between a signal generator carried by one of the movable elements and a wire vertically disposed in the hoistway.
While the prior art arrangements are effective in detecting mechanical damage to the elevator system, it would be desirable to provide a new and improved arrangement for detecting damage to an elevator system which eliminates the need for connecting a traveling cable to the counterweight, which does not depend upon detecting mechanical contact between two sensors, which does not depend upon the transmission and receiving of radio frequency energy, which does not require a battery on the counterweight, and which does not require continuous mechanical and electrical contact between a movable member and a stationary track or wire which runs the length of the hoistway.